The goal of this proposal is to use cell-fusion technology to develop a library of monoclonal xenoantibodies against the various antigenic determinants of the tumor-associated antigens synthesized by human melanoma cells (MAA). In order to achieve this, a variety of immunization approaches will be exploited and the antibodies will be tested for reactivity with a large panel of cultured normal and tumor cells lines as well as with surgically removed and normal and tumor biopsy material. The screening procedures will select antibodies to both plasma-membrane as well as cytoplasmic MAA. Various monoclonal antibodies to each MAA will be compared for their pattern of antigenically active proteolytic fragments they react with and for their ability to inhibit each other in binding assays in order to define the various determinants they identify. The individual antigenic determinants will be assessed for their protein or carbohydrate nature. Immunoadsorbents prepared with the monoclonal antibodies will be used to isolate MAA in order to generate proteolytic fragments for immunization and to determine their structural properties, emphasizing glycoprotein and glycolipid nature, subunit structure, molecular heterogeneity (identified by distribution of antigenic determinants defined by monoclonal antibodies on subpopulations of MAA) and the structural basis underlying this polymorphism. The biosynthesis, expression and shedding of various types of MAA will be investigated in cultured melanoma cells and the effects of various agents on the regulation of such processes will be studied. This information will allow a better understanind of the interactions in vivo between tumor cells and the host's immune system. Lastly, the library of monoclonal antibodies will be used to type surgically removed melanoma lesions and to assess the leves of MAA in body fluids of these patients; the results then being correlated with the clinical course of the disease. This study should lead to the development of reagents which will further analyze the changes that occur when cells undergo malignant transformation and will provide information onthe value of monoclonal antibodiesin the diagnosis and treatment of malignant diseases.